Materials for sorbing oil are in demand for cleaning up environmental oil pollution, such as oil spills on water, oil drippings on roadways, driveways or garage floors, liquid grease on food products and numerous other uses. The term oil is taken herein to mean any liquid hydrocarbon including those derived from petroleum, mineral, animal and plant sources.
Oil sorbers which have been commercially used of late include polyurethane foam, fibrous polypropylene or cellulosic material.
The polyurethane foam is an open or predominantly open cell material which suffers a number of drawbacks. One of those is that polyurethane foam will sorb water as well as oil and it is therefor necessary to prime the foam with oil so that it will preferentially sorb oil over water. This is especially important when the oil sorption is to take place at a water-oil interface since the polyurethane foam is capable of sorbing sufficient water to sink. Furthermore, polyurethane foam is relatively fragile with continued use in applications where it is desired to remove the oil by wringing and reusing the material a number of times.
Cellulosic fiber as an oil sorber is either in bulk form such as straw or in mat form made from fibers. Cellulosic fiber in its natural state (e.g. straw) is not usually considered satisfactory for an oil-water interface because the cellulosic fiber preferentially sorbs water to the substantial exclusion of oil. Cellulosic fiber may be sized to make it hydrophobic in which case its oleophilic properties remain (see for example U.S. Pat. No. 3,630,891). Even when thus formed, however, the cellulosic sorber is structurally weak and is generally unsuitable for repeated use with wringing or other mechanical oil removal between uses.
Fibrous polypropylene sorbers, (see for example U.S. Pat. No. 3,764,527) overcome much of the difficulty of polyurethane foams and cellulosic fibers in terms of preferential sorption and strength. However, they have their own drawbacks, a chief one of which is a very limited reuse potential when the oil is mechanically removed. Another problem is durability in turbulent water. While certainly better than the turbulent water durability of cellulosic materials, they still leave a great deal to be desired where used in turbulent water.